Process for preparing olefins

ABSTRACT

Olefins are manufactured by catalytically cracking a hydrocarbon feedstock by contacting said feedstock with steam at a temperature of 650*-900* C in the presence of a catalyst consisting essentially of at least 20 wt. percent of an oxide selected from the group consisting of beryllium oxide, calcium oxide and strontium oxide and the balance is aluminum oxide.

States Patent [191 Tomita et al.

[ 1 Oct. 23, 1973 [22] Filed: Nov. 22, 1971 [21] Appl No.: 200,858

[52] U.S. Cl. 208/122, 260/683.3 [51] Int. Cl. Cl0g 11/02 [58] Field ofSearch 208/122; 260/683.3,

[56] '7 References Cited UNITED STATES PATENTS 2,469,420 5 1949 Thacker260/683.3

2,311,979 2/1943 Corson et al. 260/683.3

2,289,757 7/1942 Connolly 208/122 2,422,172 6/1947 Smith et al 260/683.3

FOREIGN PATENTS OR APPLICATIONS 305,603 2/1929 Great Britain 260/683 RPrimary Examiner-Delbert E. Gantz Assistant Examiner-James W. HellwegeAttorneyWoodhams et al.

[5 7] ABSTRACT Olefins are manufactured by catalytically cracking ahydrocarbon feedstock by contacting said feedstock with steam at atemperature of 650900 C in the presence of a catalyst consistingessentially of at least 20 wt. percent of an oxide selected from thegroup consisting of beryllium oxide, calcium oxide and strontium oxideand the balance is aluminum oxide.

9 Claims, 1 Drawing Figure PROCESS FOR PREPARING OLEFINS CROSS REFERENCETO RELATED APPLICATION This application is related to our copendingapplication Ser. No. 178,264 filed Sept. 4, 197 l entitled Process forManufacturing Gaseous Mixtures Rich in hydrogen.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to the preparation of olefins from gaseous or liquidhydrocarbons. More particularly, this invention relates to thepreparation of lower olefins such as ethylene, propylene, butene andbutadiene.

2. Description of the Prior Art The most commonly employed process forpreparing lower olefins comprises introducing paraffin hydrocarbons suchas ethane, propane and butane or naphtha into an externally heated tubeto effect thermal decomposition. In this thermal decomposition process,the thermal decomposition reaction is controlled by varying thecomposition of the feed materials, the reaction temperature and/or theresidence time of the materials in the reaction tube. 5

About 30 wt. percent of ethylene, based on the amount of the feedmaterials, has been obtained from, for example, full-range naphthawithin a short reaction time by employing a high reaction temperature inorder to increase the yield of ethylene. However, such a yield is aboutthe practical upper limit and no higher yield can be expected in thethermal cracking method.

For efficient use of the starting hydrocarbons, there is a need forfurther improvement in the yield of the product olefins.

The present invention relates to a catalytic process for obtainingdesired lower olefins in a high yield at a relatively low reactiontemperature.

Various catalytic processes for the preparation of olefins have beenreported, but these processes have not been suitable for industrial usebecause of difficulties in their procedures. Catalytic processes whichhave been reported up to the present are not suited for the continuousoperation required for industrial use because even when light naphtha,which can be relatively easily treated, is used as the startingmaterial, the carbon deposition on the catalyst is remarkably high.

The present invention provides a catalytic cracking process forpreparing lower olefins,.which process can be carried out for a longperiod of time without the occurrence of carbon deposition.

We have found previously that calcination products or mixtures ofalkaline earth metal oxides, either with or without aluminum oxide, areuseful as steam reforming catalysts for obtaining hydrogen-rich gasesfrom hydrocarbons. In the course of the development of these steamreforming catalysts, we have also found that these catalysts can beused, with excellent results, in the preparation of olefins if thereaction conditions are selected properly. This unexpected result isprobably due to the property of the catalysts of preventing carbondeposition and of the property thereof of controlling thedehydrogenation reaction of the feed hydrocarbons.

SUMMARY OF THE INVENTION The catalyst used in the process of the presentinvention is a sintered product comprising (1) at least one oxideselected from the group consisting of beryllium oxide, calcium oxide andstrontium oxide and (2) aluminum oxide.

Though the functions of the respective catalyst components and thesynergism thereof have not been elucidated yet, it is known that thealkaline earth metal oxides such as beryllium oxide, calcium oxide andstrontium oxide function to control the dehydrogenation reaction of thefeed hydrocarbons and to inhibit the progress of thermal polymerization.Aluminum oxide promotes the reaction of hydrocarbons and steam. If thecatalysts are sintered or crystallized, the aluminum oxide is firmlycombined with the alkaline earth metal oxides mainly in a spinel-likestructure to increase the mechanical strength of the final moldedcatalyst.

lthas been pipposed in thepast that at temperatures ab ove 600 C., acatalyst of the foregoing type is inacti va-ted due to a rapid decreasein the hydrogen ion concentration on the surface of the catalyst withthe result being that the catalyst acts as a mere heat transfer mediumon the reactants. However, it is considered that the function ofpreventing carbon deposition by controlling the dehydrogenation reactionof hydrocarbons is due to the function of the outer shell electrons ofthe atoms constituting the catalyst and that excitation of the outershell electrons is rather promoted at high temperature. Consequently,the function of preventing carbon deposition becomes remarkable at hightemperatures. In this connection,we know from experience that acidsubstances such as silicon oxide promote carbon deposition so that suchsubstances should not be present in the catalyst used in this invention.

In the catalyst composition used in the process of the presentinvention, the capacity of alkaline earth metal oxides to prevent carbondeposition is reduced as the aluminum oxide content in the catalystincreases. Accordingly, the catalyst according to the present inventioncontains (1) at least 20 wt. percent of alkaline earth metal oxide oroxides and (2) the balance, i.e., not in excess of wt. percent, consistessentially of aluminum oxide.

FIG. 1 shows the gasification ratio of hydrocarbon, ethylene andpropylene yield in connection with the content of alkali earth metaloxides or aluminum oxide in the catalyst.

Herein,

Gasification ratio of hydrocarbons Weight of hydrocarbons below C in theproduct gas/Weight of supplied hydrocarbons X Ethylene yield Weight ofethylene in the product gas/Weight of supplied hydrocarbons X 100Propylene yield Weight of propylene in the product gas/Weight ofsupplied hydrocarbons X 100 Naphtha having C end boiling point is usedas supplied hydrocarbons under the cracking condition such as 760 C ofreaction temperature, 1.0 of H O/C ratio and 0.5 second of residencetime.

FIG. 1 shows that 20 wt. percent, preferably 30 wt. percent, of alkaliearth metal oxide in the catalyst are effective.

In the process of the present invention, a reaction temperature withinthe range of 650900 C is' suitable. When a starting material having ahigh light hydrocarbon content is used, a relatively high temperaturewithin said range is selected and, on the other hand, when a material ofhigh heavy hydrocarbon content is used, a relatively low temperaturewithin said range is employed.

The space velocity of the stream of reactants, i.e., hydrocarbonfeedstock and steam, in the reaction zone is within the range of5,00050,000 Hr, in the process of the present invention.

Table 1 shows the result by varying the residence time in the reactor atthe presence of the sintered product obtained from a mixture of calciumoxide and aluminum oxide, as a catalyst.

Catalyst composition:

CaO 51.5 wt. percent A1 47.7 wt. percent others 0.8 wt. percent Reactiontemperature: 800 C Feed: Naphtha boiling in the range of 70 180 C TABLE1 Second Yield wt. percent Hydrogen Methane Ethylene... Ethane.........Propylene Propane C Fraction Fraction above (1...... Carbon monoxide...Carbon dioxide 1 The ratio of steam to carbon in the feedstock can befrom 0.5 to /1, by weight.

Table 2 shows the result by varying H O/C in the presence of thesintered product obtained from a mixture of calcium oxide and aluminumoxide as a catalyst. Carbon deposition is not found in any case.

Catalyst composition:

CaO 51.5 wt. percent A1 0 47.7 wt. percent others 0.8 wt. percentReaction temperature: 760 C Residence time: 0.5 second Feed: Naphthaboiling in the range of The reaction pressure may be either atmosphericpressure or an elevated pressure. The operating pressure is not criticaland can be any pressure between atmospheric and 50 atm.

In the process of the present invention, there is used a reactor havingat least one of a fixed catalyst bed, a fluidized catalyst bed and ajetted catalyst bed.

The heat of reaction may be supplied by an external heating system inwhich the reactor is heated by heat supplied through a heat transferwall or by an internal heating system in which a proper quantity ofoxygen or oxygen rich air is fed into the reactor and heat generated bypartial oxidation of the starting materials is used.

The presence of impurities, such as sulfur, in the starting materialsdoes not influence the reaction. Therefore, no limitation on thecomposition of the starting materials within those ranges normallyoccurring in conventional petroleum oil materials is necessary. Theinvention can be practiced with heavy oils, such as crude oil includinghigh sulfur crudes, naphtha, kerosene, light oil fractions derived fromcrudes and mixtures thereof.

The invention will be further described by the following examples whichare given to illustrate, but not limit, the invention.

In the following Examples, the reactor used was a tube of 30 mm. innerdiameter and 1,000 mm. length prepared by centrifugal casting and filledwith a catalyst in the form of approximately cylindrical pellets of 5mm. diameter and 5 mm. thickness. The reactor was heated externallythrough the tube wall.

EZ AME L J,

Naphtha boiling in the range of -l C was catalytically cracked in thepresence of the sintered product obtained from a mixture of berylliumoxide and aluminum oxide. The results were as follows.

Catalyst composition: BeO 20.1 wt. percent, A1-

O 79.8 wt. percent, others 1.1 wt. percent Temperature of the gasproduct evolved from the reactor: 720 C Ratio (by weight) of steam tocarbon in the material fed into the reactor: 3:1 Residence time in thereactor: 0.7 second Composition of resulting gas product (wt. percentbased on the starting material): Hydrogen 2.2 Methane 11.1 Ethylene-50.2

Ethane 2.1 Propylene-- 14.2 Propane 0.5

C, fraction- 4.9

Fraction above C.,l 1.9 Carbon Monoxide 0.4

Carbon dioxide 12.4 w

EXAMPLE 2 Four varieties of hydrocarbon, as described below, werecatalytically cracked in the presence of the sintered product obtainedfrom a mixture of calcium oxide and aluminum oxide, as a catalyst, toobtain olefins. The results were as follows.

Catalyst compositionz C aO 51.5 wt. percent, A1 0 47.7w. percent, others 0. 8 wt. percent if w Temperature of the gaseous product evolvedfrom the reactor: 720 C 5 Ratio (by :weight)-of steam to carbon inthermaterial fed into-the reactor: 3:1 Residence-time in thereactor:-0.7 second Composition of the vresulting gas (wt. percent basedon the starting material): a. When ethane of 99.5% purity was usedasstarting material:

Hydrogen 4.8 Methane4.0 Ethylene-42.2 Ethane-47.0 Propylene- 1 .0 Carbonmonoxide-0.1 Carbon dioxide-3 .5 b. 'When naphtha boiling in the rangeof 70"180C was used .as starting material: .Hydrogen-2.3 Methane-l 2.3Ethylene-48.4 Ethane-2.4 *Propylene--l3 .4 Propane-0.4 C Fraction-4.7Fra'ction above =C -:l2.2 Carbon monoxide-:6 Carbon dioxide-13:6 When apetroleum :fraction boilingin'the range 0f 250-'400*C was vused asstarting material: Hydrogen 1 .3 Methane-9.5 Ethylene-41.3 Ethane-1.8Propylene-11.2 .Propane0.3 C Fraction6.5 Fraction above C.,l5.0 Carbonmonoxide0.8 Carbon dioxide-15.3

rial: Hydrogen 1.2 Methane9.2 Ethylene-38.8 Ethane l .5 Propylene10.8Propane-0.2 C Fraction8.6 Fraction above C -29.8 Carbon monoxide0.7Carbon dioxide-14. 9

EXAMPLE 3 Naphtha boiling in the range of 70 180 C was cata lyticallycracked in the presence of the sintered product obtained from a mixtureof strontium oxide and aluminum oxide a sa catalyst. The results were asfollows: Catalyst composition: SrO 49.0 wt. percent, A1 0 50.0 wt.percent, others 1.0 wt. percent Temperature of the gaseous productevolved from the reactor: 720 C Ratio (by weight) of steam to carbon inthe material fed into the reactor: 3:1 Residence time in the reactor:0.7 second Composition of the resulting gas product (wt. percent basedon the starting material): Hydrogen-2.0 Methane-l0.6 Ethylene--50.8

Ethane-215 When Kuwait crude oilwas used as starting mate- Propylene-16.2 Propane-0.7 C Fraction-5.7 Fraction above C.,-l6.0 =Carbonmonoxide-0.2 Carbon dioxide9.7

EXAMPLE '4 V Naphtha-boiling in the range of 1'80Cwascatalyticallycracked in the presence of the sintered .product'obtainedfrom a mixture of *beryllium oxide, cal- .ciumoxide-andaluminum oxide,as a catalyst. The results "-were as'follows:

Catalyst compositions-BeO 6.2 wt.- percent,CaO 32.8

wt. percent, A1 0 61.0 'wt. percent Temperature of the gaseous product"evolved from the reactor: 720C *Ratio (by weight) of steam to carbon inthe material fed into the reactor: 3:] Residence time in the reactor:0.7 second Composition of resulting -gas'(wt. percent based on thestarting material):

Hydrogen-2;] Methane- 10.8 Ethylene50.5 Ethane-2.6 Propylene-15.8Propane-0:6 *C Fraction-5.8 :F-raction above C 15.7 Carbon monoxide-0.2Carbon dioxide-9.8

EXAMPLE 5 N apht haboiling in the range of 70-l C was catalyticallycracked in the presence of the sintered product obtained from a mixtureof beryllium oxide, strontium oxide and aluminum oxide, as acatalys't.The results were are follows:

Catalyst composition BeO 6.4 wt. percent, SrO 30.8

wt. percenfA'l 'fi ff ii/t percent Temperatureof the gaseous productevolved from the reactor: 720 C Ratio (by weight) of steam to carbon inthe material fed into the reactor: 3:1 Residence time in the reactor:0.7 second Composition of resulting gas (wt. percent based on thestarting material): Hydrogen-2.4 Methane- 10.8 Ethylene-5 l .2Ethane-2.4 Propylene- 1 5.8 Propane0.6 C Fraction-5.8 Fraction above C-17.0 Carbon monoxide0.2 Carbon dioxide-9.8

EXAMPLE 6 Naphtha boiling in the range of 70-180C was catalyticallycracked in the presence of the sintered product obtained from a mixtureof calcium oxide, stron- 5 tium oxide and aluminum oxide, as a catalyst.The re- 19.2 wt. percentjxlgg 39.8 wt: percent Temperature of thegaseous product evolved from the reactor: 680 C Ratio (by weight) ofsteam to carbon in the material fed into the reactor: 3:1 Residence timein the reactor: 0.7 second Composition of resulting gas (wt. percentbased on the starting material): Hydrogen1.9 Methane 10.2 Ethylene-52.5Ethane2.5 Propylene16.3 Propane-0.7 C Fraction-6.5 Fraction $573750;-T512 Carbon monoxide0.2 Carbon dioxide-9.2

EXAMPLE 7 Naphtha boiling in the range of 70-1 80 C was cata lyticallycracked under pressure in the presence of the sintered product obtainedfrom a mixture of calcium oxide and aluminum oxide, as a catalyst. Theresults were as follows:

Catalyst composition: CaO 51.5 wt. percent, A1503 47.7 wt. percent,others 0.8 wt. percent Temperature of the gaseous product evolved fromthe reactor: 720 C Pressure in the reactor: 10 kg/cm G Ratio (by weight)of steam to carbon in the material fed into the reactor: 3:1 Residencetime in the reactor: 0.7 second Composition of resulting gas (wt.percent based on the starting material): Hydrogen-2.4 Methane- 18.2Ethylene-43.5 Ethane-3.1 Propylene-1 1.8 Propane-02 C Fraction4.5Fraction above C -12.8 Carbon monoxide0.8 Carbon dioxide-15.1

EXAMPLE 8 Naphtha boiling in the range of 701 80C was catalyticallycracked under pressure in the presence of the sintered product obtainedfrom a mixture of calcium oxide,and aluminum oxide, as a catalyst. Theresults were as follows: 7 W

Catalyst composition: CaO 51.5 wt. percent, A1

47.7 wt. percent, others 0.8 wt. percent, Temperature of the gaseousproduct evolved from the reactor: 720 C Pressure in the reactor: 30kg/cm G Ratio (by weight) of steam to carbon in the material fed intothe reactor: 3:1 Residence time in the reactor: 0.7 second Compositionof resulting gas (wt. percent based on the starting material):Hydrogen2.5 Methane2l.3 Ethylene-41.2 Propylene-9.8 Propane0.1 CFraction-4.5 Fraction above C -1 1.9 Carbon monoxide-0.9

Carbon dioxide 18.1

EXAMPLE 9 Naphtha boiling in the range of -l C was catalytically crackedin the presence of the sintered product obtained from a mixture ofberyllium oxide, calcium oxide, strontium oxide and aluminum oxide, as acatalyst. The results were as follows:

Catalyst composition: BeO 4.3 wt. percent CaO 1 1.4 wt. percent, SrO20.8 wt. percent, A 63.6 wt. percent Temperature of the gaseous productevolved from the supply fed into the reactor: 720 C Ratio (by weight) ofsteam to carbon in the material fed into the reactor: 3:1

Residence time in the reactor: 0.7 second Composition of resulting gas(wt. based on the starting material):

Hydrogen-2.3 Methane 10.7 Ethylene5 1.7 Ethane2.4 Propylene-- 15.2Propane-0.5

C Fraction-5.7 Fraction above C,,l6.2 Carbon monoxide-0.2 Carbondioxidel0.0

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A process for manufacturing olefins by catalytically cracking afeedstock of normally gaseous or liquid hydrocarbons, which comprisescontacting said feedstock with steam, the weight ratio of steam/carbonin said feedstock being in the range of 0.5 to 10/1, at a temperature inthe range of 650-900 C. and in the presence of a catalyst consistingessentially of a sintered product containing (1) at least about 20weight percent of at least one oxide selected from the group consistingof beryllium oxide, calcium oxide and strontium oxide and (2) thebalance is aluminum oxide.

2. A process according to claim 1, wherein the sintered catalyst is amixture of aluminum oxide and beryllium oxide.

3. A process according to claim 1, wherein the sintered catalyst is amixture of aluminum oxide and calcium oxide.

4. A process according to claim 1, wherein the sintered catalyst is amixture of strontium oxide and aluminum oxide.

5. A process according to claim 1, wherein the sintered catalyst is amixture of beryllium oxide, calcium oxide and aluminum oxide.

6. A process according to claim 1, wherein the sintered catalyst is amixture of beryllium oxide, strontium oxide and aluminum oxide.

7. A process according to claim 1, wherein the sintered catalyst is amixture of calcium oxide, strontium oxide and aluminum oxide.

8. A process according to claim 1, wherein the sintered catalyst is amixture of beryllium oxide, calcium oxide, strontium oxide and aluminumoxide.

9. A process according to claim 1, in which the space velocity of thestream of reactants in the reaction zone is in the range of 5,000 to50,000 hr.

2. A process according to claim 1, wherein the sintered catalyst is amixture of aluminum oxide and beryllium oxide.
 3. A process according toclaim 1, wherein the sintered catalyst is a mixture of aluminum oxideand calcium oxide.
 4. A process according to claim 1, wherein thesintered catalyst is a mixture of strontium oxide and aluminum oxide. 5.A process according to claim 1, wherein the sintered catalyst is amixture of beryllium oxide, calcium oxide and aluminum oxide.
 6. Aprocess according to claim 1, wherein the sintered catalyst is a mixtureof beryllium oxide, strontium oxide and aluminum oxide.
 7. A processaccording to claim 1, wherein the sintered catalyst is a mixture ofcalcium oxide, strontium oxide and aluminum oxide.
 8. A processaccording to claim 1, wherein the sintered catalyst is a mixture ofberyllium oxide, calcium oxide, strontium oxide and aluminum oxide.
 9. Aprocess according to claim 1, in which the space velocity of the streamof reactants in the reaction zone is in the range of 5,000 to 50,000 hr1.